We've had some more reports about this sort of activity in the past few days, where small purchases are being contested for outlandish amounts of money in chargebacks. It is likely that some scammers have found a way to exploit PayPal's dispute system.
We do not process any of the transactions or refunds on our side, so we cannot take any action from here. The safe processing of online payments is PayPal's entire job and we'll have to rely on them to take care of this problem.
Any records PayPal might need about your original orders are available in your E-junkie transaction logs to help resolve these disputes.
So far it sounds like PayPal only reverses the original amount of the purchase in the end, but if they apply any other fees as a result of these scam chargebacks I'd recommend escalating the issue with PayPal since these scam purchases only occurred to exploit a flaw in their system.